Imaging the Whole-Lithosphere Architecture of a Mineral System-Geophysical Signatures of the Sources and Pathways of Ore-Forming Fluids

Mineral systems can be thought of as a combination of several critical elements, including the whole-lithosphere architecture, favorable geodynamic/tectonic events, and fertility. Because they are driven by processes across various scales, exploration benefits from a scale-integrated approach. There are open questions regarding the source of ore-forming fluids, the depth of genesis, and their transportation through the upper crust to discrete emplacement locations. In this study, we investigate an Au-Cu metal belt located at the margin of an Archean-Paleoproterozoic microcontinent. We explore the geophysical signatures by analyzing three-dimensional models of the electrical resistivity and shear-wave velocity throughout the lithosphere. Directly beneath the metal belt, narrow, vertical, finger-like low-resistivity features are imaged within the resistive upper-middle crust and are connected to a large low-resistivity zone in the lower crust. A broad low-resistivity zone is imaged in the lithospheric mantle, which is well aligned with a zone of low shear-wave velocity, examined with a correlation analysis. In the upper-middle crust, the resistivity signatures give evidence for ancient pathways of fluids, constrained by a structure along a tectonic boundary. In the lower lithosphere, the resistivity and velocity signatures are interpreted to represent a fossil fluid source region. We propose that these signatures were caused by a combination of factors related to refertilization and metasomatism of the lithospheric mantle by long-lived subduction at the craton margin, possibly including iron enrichment, F-rich phlogopite, and metallic sulfides. The whole-lithosphere architecture controls the genesis, evolution, and transport of ore-forming fluids and thus the development of the mineral system.